There are conventional component placement machines which holds and carries a component from a component feeding unit to above a fixed board, and lowers the component to mount the component on the board. The placement machine is required to reproduce a position where the component being held is placed in X-Y directions (a horizontal plane). On the other hand, it is also required to carry the component from the component feeding unit to above the board, position the component in X-Y directions, and return to the component feeding unit after placing the component as quick as possible in order to increase productivity of the mount board.
The component placement machine is thus constructed with Y beams fixed to a base and extending along a Y axis, an X beam installed on the Y beams so as to be slidable along the Y beam, and a head installed on the X beam so as to be slidable along the X beam.
Here, the X beam is provided with rails which lineally guide the head by allowing the head to slide directly along the rails. The rails, which have friction with the head, contain, as a material, a metal which is heavy and resistant to the friction, for example. The X beam, which supports the rails and the head, has a high structural strength and contains a metal having a lighter weight as a material, so that the weight of the members which move along the Y beams is saved.
However, as the rails extending along an X axis and the X beam are made of different metals and joined together, the X beam bends due to a bimetallic effect when there is a change in temperature of the component placement machine. Such bend of the X beam makes it difficult for the component placement machine to accurately place components on a board and requires correction of data for moving the head in consideration of the bend, and therefore has a negative impact on the productivity of the component placement machine.
The techniques disclosed in PTL1, PTL2, and PTL3 prevent an X beam from bending by bar-shaped reinforcement members which are made of the same material as the rails and provided on a side of the X beam opposite to the side on which rails are mounted. Bends of the rails and the X beam are thus compensated by bends of the reinforcement members the X beam, so that the straightness of the rail is retained.